Since both sets of spam came from the same account and you changed your password in the intervening time I wonder if your e-mail addresses wasn't spoofed this time rather than hacked. One clue might be in your Sent e0mail folder. If copies of the problem e-mails aren't there spoofing is a possibility. See this lifehacker article for some ideas.

Some of our more networking/server savy members may come up with other ideas or even correct mistakes on my part.

After reading your post, I decided to check my sent mail folder, and what I found was actually very interesting....

The email was indeed in my sent mail folder, however next to the name, it had that little security warning from Gmail that states "This message may not have been sent by (my email)" Then it shows a completely different name than mine, followed by my email address in captions. Very interesting indeed, I'm not quite sure what to make of it...